The present disclosure relates to a vapor deposition mask substrate, a method for manufacturing a vapor deposition mask substrate, and a method for manufacturing a vapor deposition mask.
A vapor deposition mask includes a first surface and a second surface. The first surface faces a target such as a substrate, and the second surface is opposite to the first surface. The holes extending through the first and second surfaces each include a first opening, which is located in the first surface, and a second opening, which is located in the second surface. The vapor deposition material entering the holes through the second openings forms on the target a pattern corresponding to the position and shape of the first openings (see Japanese Laid-Open Patent Publication No. 2015-055007, for example).
Each hole of the vapor deposition mask has a cross-sectional area that increases from the first opening toward the second opening. This increases the amount of vapor deposition material entering the hole through the second opening so that an adequate amount of vapor deposition material reaches the first opening. However, some of the vapor deposition material entering the hole through the second opening adheres to the wall surface defining the hole, failing to reach the first opening. The vapor deposition material adhering to the wall surface defining the hole may prevent other vapor deposition material from reaching the first opening, lowering the dimensional accuracy of the pattern.
To reduce the amount of vapor deposition material adhering to the wall surfaces defining holes and thereby increase the dimensional accuracy of the pattern, a structure has been contemplated in which the thickness of the vapor deposition mask is reduced to reduce the areas of the wall surfaces defining holes. In order to reduce the thickness of the vapor deposition mask, a technique is used to reduce the thickness of the metal sheet for manufacturing the vapor deposition mask. However, in the process of etching the metal sheet to form holes, a smaller thickness of the metal sheet results in a smaller amount of metal to be etched. This shortens the permissible range of the duration for which the metal sheet is in contact with the etchant, increasing the difficulty in achieving the required dimensional accuracy of the first and second openings. In particular, the manufacturing of metal sheet involves a rolling step, in which the base material is drawn with rolls, or an electrolysis step, in which the metal sheet deposited on an electrode is peeled off from the electrode. Accordingly, the metal sheet has an undulated shape in which different positions in the metal sheet have different elongation difference ratios. Different positions of an undulated metal sheet are brought into contact with the etchant often for different durations. As described above, although a thinner vapor deposition mask reduces the amount of vapor deposition material adhering to the wall surfaces defining holes and thereby increases the dimensional accuracy of the patterns in repeated vapor deposition, such a vapor deposition mask tends to lack the required dimensional accuracy of the holes, causing another problem that the required dimensional accuracy of the pattern in each vapor deposition is difficult to achieve.